Incontinence measurement sensor

ABSTRACT

Urinary incontinence can be evaluated both in respect of frequency and quantity by use of a detector device in the form of a flexible sheet of absorbent material having elongate electrodes supported in it in an interleaved, uniformly spaced array. This device is worn as a diaper and any incontinence will vary and be detectable and measurable by the electrical conductivity of the sheet material between the electrodes. Any undesirable variations in this technique due to compression of the sheet in use can be offset by supporting the electrodes in a waved manner along their lengths and through the sheet thickness, and by quilting the sheet. Other variations due to differing urine salts content can be taken into account by pre-loading the sheet with a salt to give a datum or bias salt level above which such variations are less significant.

United States Patent 11 1 Flack et al.

1451 Sept. 18, 1973 INCONTINENCE MEASUREMENT SENSOR [75] Inventors:Frederick Colin Flack; Evan Douglas James, both of Devon, England [73]Assignee: National Research Development Corporation, London, England 22Filed: Apr. 23, 1971 21 Appl No.: 136,710

[30] Foreign Application Priority Data 128/2 R, 2.1 R, 2.1 Z, 138 A [56] References Cited Australia 128/138 A France 128/138 A PrirriaryExaminer-William E. Kamm Attorney--Cushman, Darby & Cushman [57]ABSTRACT Urinary incontinence can be evaluated both in respect offrequency and quantity by use of a detector device in the form of aflexible sheet of absorbent material having elongate electrodessupported in it in an interleaved, uniformly spaced array. This deviceis worn as a diaper and any incontinence will vary and be detectable andmeasurable by the electrical conductivity of the sheet material betweenthe electrodes. Any undesirable variations in this technique due tocompression of the sheet in use can be offset by supporting theelectrodes in a waved manner along their lengths and UNITED STATESPATENTS through the sheet thickness, and by quilting the sheet.3,245,068 4/1966 wegryn at al- 2838 A Other variations due to differingurine salts content can 3 085 566 4/1963 Tones n be taken mto account bypre-loadmg the sheet with a 2,1271538 8/1938 Seiger [28/138 A Salt togive a datum bias Sal! level above which Such t' l i 'f' t. FOREIGNPATENTS 0R APPLICATIONS are 1,174,346 12/1969 Great Britain 128/138 A 6Claims, 2 Drawing Figures THICKER, HIGHER ABSORBENCY SHEET METAL THREAD4 LA ER ELECTRODE BACKING 1 THREAD THINNER, LESSER ABSORBENCY 3 SHEETBACKl NG LAYER PATENTEDSEPI 8 I973 FIGI ABSORBENCY SHEET METAL THREADELECTRODE THICKER, HIGHER LAYER THINNER, LESSER AB'S'ORBENCY/ SHEETBACKING LAYER INCONTINENCE MEASUREMENT SENSOR Various proposals havebeen made in connection with the treatment of urinary incontinence. Forexample, diaper-like devices have been proposed to render the results ofsuch incontinence less inconvenient, mechanically operable devices to beworn internally or externally have been proposed whereby suchincontinence may be controlled, implantable devices to enhance musclecontrol by electrical stimulation have also been proposed for urinaryincontinence control purposes, and devices to give alarm or shocktherapy have been proposed for enuresis.

Most of these various devices are used in practice and they can attaintheir objects in appropriate circumstances. However, there are differentforms of urinary incontinence and the choice of device, or moregenerally the treatment to be adopted for an incontinent patient shouldnaturally depend on the form of incontinence at hand. There is, though,often difficulty in deciding on what form of incontinence is to be dealtwith. This difficulty arises from the fact that one of the main factorsrelied upon is the patient's own observations, but the patient, usuallybeing a member of the lay public, cannot be relied upon to observe asaccurately as trained personnel.

An object of the present invention is to reduce this area of difficultyby providing a device whereby urinary incontinence can be observedindependently, without embarrassment or significant inconvenience to thepatient.

To this end, the invention provides, in a more general aspect thereof, adevice comprising a flexible sheet of absorbent material having a pairof elongate electrodes supported therein in an'interleaved, uniformlyspaced array. The electrode array will normally span a major, or atleast significant area of the sheet for this purpose each electrode maycomprise a plurality of parallel limbs connected at one end to a commonterminal conductor, the limbs of the respective electrodes beinginterleaved in an alternating sequence. Other geometricalconfigurations, such as interleaved spirals, for example, may be equallysuitable.

In use of such a device, it will normally be worn by a patient in themanner of a diaper, although the sheet can also be appropriately locatedin a cot or bed, and the two terminal conductors are subjected to a lowvoltage alternating current. Then, when urine loss occurs, a zone of theelectrode area becomes moistened and the resultant change in electricalconductivity can be detected, and indicated and/or recorded, by suitableinstruments coupled to the device. It is preferable to record signalsrepresenting both the time (to denote frequency) and magnitude of urineloss, as by a pen recorder or other suitable instrument. It is alsopreferable that a record be made simultaneously concerning the physicalattitude or activity of the patient at least when urine loss occurs.This function can be carried out simply by an observer in conjunctionwith the firstmentioned instrumentation, although it may be desirable toadd further instrumentation responsive to a strain gauge or other formof transducer connected to the patient to indicate activity.

In any event, in a more particular aspect the invention provides urinaryincontinence measuring apparatus comprising a device together withenergisation means and instrumentation as described above. It is to benoted that such a device and associated energisation means andinstrumentation can be coupled by leads where complete freedom ofmobility for the patient is not required, while the coupling can be byradio telemetry when complete freedom is required (to reduce the risk ofaccident involving leads where the patient is an infant or sleeping,say), the energisation means being carried with the device together witha suitable transmitter. It may also be possible, as another alternative,for the instrumentation to be carried with the device and energisationmeans on the patient, the instrumentation comprising a miniature taperecorder, say.

Certain more particular features have been found preferable for thedevice during development of the invention. For example, it is desirablethat the sheet material should absorb and spread liquid in the plane ofthe sheet sufficiently rapidly to afford a capacity which does not leadto saturation at a level of urine loss which is too low for a moregeneral use of the invention. However, this requirement will normallyentail the use of sheet material which is significantly thicker than theelectrode material, the latter being relatively thin to give theflexibility and comfort compatible with effective use of the device asan under-garment. This leads to a possible difficulty in that theelectrical conductivity between the electrodes may vary for a givenlevel of urine loss as a function of the compression of the sheet whichis variable, in turn, in dependence upon patient activity.

This possible difficulty is reduced in a preferred form of the device,representing another more particular aspect of the invention, bysupporting the electrodes in a generally cyclically varying waveshapeextending along the electrode lengths and through the thickness of thesheet. A suitable manner of obtaining such an electrode waveshape is bysewing the sheet with the electrode material serving as the thread in aconven tional stitching mechanism.

It has also been found useful in this same connection to quilt the sheetof the device since this can serve to reduce the effects of variablecompression without unduly restricting the desired lateral absorbency ofthe sheet. Quilting is additionally useful in serving to stabilise thepositions of the electrodes in the sense of their mutual spacing, andthe quilting is conveniently effected by lines of stitching uniformlyspaced between adjacent electrode lengths.

A further difficulty can arise by variation of electrical conductivitywith urine salts content. This variation, can arise not only betweendifferent individuals, but also between different times of the day for agiven individual. Magnitudes of variation have been measured which areequivalent to that between a 0.5 percent and 1.5 percent (by weight)aqueous sodium chloride solution, and these can clearly introduce errorinto any quantitative measure obtained by use of the invention.

In accordance with a further more particular aspect of the. inventionthis last difficulty is reduced by preloading of the device with salt inany appropriate manner before use to provide a dry device impregnatedwith salt whereby signals representing the level of incontinence areeffectively biased to a predetermined level which is relativelyindependent of urine salts content. A suitable pre-loading for thispurpose is approximately equivalent to a 5 percent (by weight) aqueoussodium chloride solution saturating the sheet. This level of pre-loadinghas been found suitable in giving a satisfactory bias without swampingthe singal variations of interest or causing skin irritation.

In development of the present invention to date, devices as describedabove have been used repeatedly with appropriate cleansing and freshpro-loading be- BRIEF DESCRIPTION OETHE DRAWING FIG. 1 is a diagrammatictop plan view of a device constructed in accordance with the presentinvention; and

FIG. 2 is a vertical cross-sectional view through a portion of the sheetof the device.

DETAILED DESCRHTION OF THE PRESENTLY PREFERRED EMBODIMENT In the drawingthe device is denoted at 1 and comprises a multi-layered sheet of cottonmesh 2 of strip form measuring approximately 18 X 5 ins. The sheet isbacked by a layer of nylon cloth 3 which is less readily permeable byliquid than the cotton mesh and serves to assist the lateral spread andabsorption of liquid as mentioned earlier.

The electrode array is provided by surgical stainless steel wire, ofabout 36 qauge, stitched to the sheet parallel to the longitudinal axisthereof in six lengths at equal spacing of about 0.5 in. This wire isdenoted by chain lines 4 from which it will be seen that two interleavedelectrodes with three limbs each are formed by connecting the associatedlimbs at opposite ends of the sheet t respectively different conductorsof a twin lead 5. The lead 5 is connected to the electrode limb wires bycrimping or in any other suitable manner and is held to the sheet byoverlapping the backing sheet to provide a stitched marginal tunnelthrough which the conductors run. The sheet is also stitchedlongitudinally with thread intermediate to the electrode limbs asdenoted in broken line at 6.

The lead 5 is powered at about 30 mV through an A.C. coupling 7 by a2Kc/s oscillator 8. The lead is also connected across measuring andrecording apparatus including a differential amplifier 9, a meter 10'and a pen recorder 11. The electrode array and sheet act as a variableresistor denoted in broken line at 12 and having a value less than whenthe sheet is fully saturated in the present example.

We claim 1. A urinary incontinence detector device comprisa sheet ofabsorbent material; a dry salt dispersion in said sheet to preload thesheet whereby, when moistened with urine, the natural salt content ofurine is not a significant factor in changing the electrical conductanceof the sheet; a pair of elongate electrodes connected to said sheet in auniformly spaced array extending over a major area of said sheet; andterminals for connecting said electrodes to an electrical conductanceindicator.

2. A device according to claim 1 wherein each of said electrodescomprises a plurality of parallel limbs each connected at one end to acommon terminal conductor, the limbs of the respective electrodes beinginterleaved in an alternating sequence.

3. A device according to claim 1 wherein said electrodes are supportedin said sheet in a generally cyclically varying waveshape extendingalong their lengths and through the thickness of said sheet, whichwaveshape is of short length compared to the planar dimensions of saidsheet.

4. A device according to claim 1 wherein said sheet is oflaminated formcomprising a thicker layer of a first absorbent material to enhance thespread of urine through the plane of said thicker layer and thereby actagainst local saturation therein, a second layer of different absorbentmaterial having a lesser liquid permeability than said first material,said second layer backing said first layer.

5. A device according to claim 1 wherein said sheet is quilted alonglines which are uniformly spaced between adjacent lengths of saidelectrodes.

6. A device according to claim 1 wherein said salt dispersion isapproximately equivalent in electrical conductance to that of the saltin a 5 percent, by weight, aqueous sodium chloride solution saturatingsaid sheet.

1. A urinary incontinence detector device comprising: a sheet ofabsorbent material; a dry salt dispersion in said sheet to preload thesheet whereby, when moistened with urine, the natural salt content ofurine is not a significant factor in changing the electrical conductanceof the sheet; a pair of elongate electrodes connected to said sheet in auniformly spaced array extending over a major area of said sheet; andterminals for connecting said electrodes to an electrical conductanceindicator.
 2. A device according to claim 1 wherein each of saidelectrodes comprises a plurality of parallel limbs each connected at oneend to a common terminal conductor, the limbs of the respectiveelectrodes being interleaved in an alternating sequence.
 3. A deviceaccording to claim 1 wherein said electrodes are supported in said sheetin a generally cyclically varying waveshape extending along theirlengths and through the thickness of said sheet, which waVeshape is ofshort length compared to the planar dimensions of said sheet.
 4. Adevice according to claim 1 wherein said sheet is of laminated formcomprising a thicker layer of a first absorbent material to enhance thespread of urine through the plane of said thicker layer and thereby actagainst local saturation therein, a second layer of different absorbentmaterial having a lesser liquid permeability than said first material,said second layer backing said first layer.
 5. A device according toclaim 1 wherein said sheet is quilted along lines which are uniformlyspaced between adjacent lengths of said electrodes.
 6. A deviceaccording to claim 1 wherein said salt dispersion is approximatelyequivalent in electrical conductance to that of the salt in a 5 percent,by weight, aqueous sodium chloride solution saturating said sheet.